/*
 * Copyright 2024-2025 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.alibaba.cloud.scheduling.schedulerx.util;

import java.text.ParseException;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Locale;
import java.util.Map;
import java.util.SortedSet;
import java.util.StringTokenizer;
import java.util.TimeZone;
import java.util.TreeSet;

import org.springframework.util.Assert;

/**
 * @author yaohui
 */
public final class CronExpression {

	protected static final int SECOND = 0;
	protected static final int MINUTE = 1;
	protected static final int HOUR = 2;
	protected static final int DAY_OF_MONTH = 3;
	protected static final int MONTH = 4;
	protected static final int DAY_OF_WEEK = 5;
	protected static final int YEAR = 6;
	protected static final int ALL_SPEC_INT = 99; // '*'
	protected static final int NO_SPEC_INT = 98; // '?'
	protected static final Integer ALL_SPEC = ALL_SPEC_INT;
	protected static final Integer NO_SPEC = NO_SPEC_INT;

	protected static final Map<String, Integer> monthMap = new HashMap<>(20);
	protected static final Map<String, Integer> dayMap = new HashMap<>(60);

	static {
		monthMap.put("JAN", 0);
		monthMap.put("FEB", 1);
		monthMap.put("MAR", 2);
		monthMap.put("APR", 3);
		monthMap.put("MAY", 4);
		monthMap.put("JUN", 5);
		monthMap.put("JUL", 6);
		monthMap.put("AUG", 7);
		monthMap.put("SEP", 8);
		monthMap.put("OCT", 9);
		monthMap.put("NOV", 10);
		monthMap.put("DEC", 11);

		dayMap.put("SUN", 1);
		dayMap.put("MON", 2);
		dayMap.put("TUE", 3);
		dayMap.put("WED", 4);
		dayMap.put("THU", 5);
		dayMap.put("FRI", 6);
		dayMap.put("SAT", 7);
	}

	private final String cronExpression;
	private TimeZone timeZone = null;
	protected transient TreeSet<Integer> seconds;
	protected transient TreeSet<Integer> minutes;
	protected transient TreeSet<Integer> hours;
	protected transient TreeSet<Integer> daysOfMonth;
	protected transient TreeSet<Integer> months;
	protected transient TreeSet<Integer> daysOfWeek;
	protected transient TreeSet<Integer> years;

	protected transient boolean lastdayOfWeek = false;
	protected transient int nthdayOfWeek = 0;
	protected transient boolean lastdayOfMonth = false;
	protected transient boolean nearestWeekday = false;
	protected transient int lastdayOffset = 0;
	protected transient boolean expressionParsed = false;

	/**
	 * MAX_YEAR.
	 */
	public static final int MAX_YEAR = Calendar.getInstance().get(Calendar.YEAR) + 100;

	/**
	 * MIN_CAL.
	 */
	public static final Calendar MIN_CAL = Calendar.getInstance();

	static {
		MIN_CAL.set(1970, 0, 1);
	}

	/**
	 * MIN_DATE.
	 */
	public static final Date MIN_DATE = MIN_CAL.getTime();

	/**
	 * Constructs a new <CODE>CronExpression</CODE> based on the specified
	 * parameter.
	 *
	 * @param cronExpression String representation of the cron expression the
	 *                       new object should represent
	 * @throws ParseException if the string expression cannot be parsed into a valid
	 *                        <CODE>CronExpression</CODE>
	 */
	public CronExpression(final String cronExpression) throws ParseException {
		if (cronExpression == null) {
			throw new IllegalArgumentException("cronExpression cannot be null");
		}

		this.cronExpression = cronExpression.toUpperCase(Locale.US);

		buildExpression(this.cronExpression);
	}

	/**
	 * Indicates whether the given date satisfies the cron expression. Note that
	 * milliseconds are ignored, so two Dates falling on different milliseconds
	 * of the same second will always have the same result here.
	 *
	 * @param date the date to evaluate
	 * @return a boolean indicating whether the given date satisfies the cron
	 * expression.
	 */
	public boolean isSatisfiedBy(final Date date) {
		final Calendar testDateCal = Calendar.getInstance(getTimeZone());
		testDateCal.setTime(date);
		testDateCal.set(Calendar.MILLISECOND, 0);
		final Date originalDate = testDateCal.getTime();

		testDateCal.add(Calendar.SECOND, -1);

		final Date timeAfter = getTimeAfter(testDateCal.getTime());

		return ((timeAfter != null) && (timeAfter.equals(originalDate)));
	}

	/**
	 * Returns the next date/time <I>after</I> the given date/time which
	 * satisfies the cron expression.
	 *
	 * @param date the date/time at which to begin the search for the next valid
	 *             date/time
	 * @return the next valid date/time.
	 */
	public Date getNextValidTimeAfter(final Date date) {
		return getTimeAfter(date);
	}

	/**
	 * Returns the next date/time <I>after</I> the given date/time which does
	 * <I>not</I> satisfy the expression.
	 *
	 * @param date the date/time at which to begin the search for the next
	 *             invalid date/time
	 * @return the next valid date/time.
	 */
	public Date getNextInvalidTimeAfter(final Date date) {
		long difference = 1000;

		//move back to the nearest second so differences will be accurate
		final Calendar adjustCal = Calendar.getInstance(getTimeZone());
		adjustCal.setTime(date);
		adjustCal.set(Calendar.MILLISECOND, 0);
		Date lastDate = adjustCal.getTime();

		Date newDate;

		//FUTURE_TODO: (QUARTZ-481) IMPROVE THIS! The following is a BAD solution to this problem. Performance will be very bad here, depending on the cron expression. It is, however A solution.

		//keep getting the next included time until it's farther than one second
		// apart. At that point, lastDate is the last valid fire time. We return
		// the second immediately following it.
		while (difference == 1000) {
			newDate = getTimeAfter(lastDate);
			if (newDate == null) {
				break;
			}

			difference = newDate.getTime() - lastDate.getTime();

			if (difference == 1000) {
				lastDate = newDate;
			}
		}

		return new Date(lastDate.getTime() + 1000);
	}

	/**
	 * Returns the time zone for which this <code>CronExpression</code>
	 * will be resolved.
	 *
	 * @return the time zone.
	 */
	public TimeZone getTimeZone() {
		if (timeZone == null) {
			timeZone = TimeZone.getDefault();
		}

		return timeZone;
	}

	public void setTimeZone(final TimeZone timeZone) {
		this.timeZone = timeZone;
	}

	@Override
	public String toString() {
		return cronExpression;
	}

	/**
	 * check cron expression is valid or not.
	 *
	 * @param cronExpression cron expression
	 * @return return{@code true}if Cron expression is valid，otherwise return{@code false}.
	 */
	public static boolean isValidExpression(final String cronExpression) {
		try {
			new CronExpression(cronExpression);
		}
		catch (final ParseException pe) {
			return false;
		}
		return true;
	}

	public static void validateExpression(final String cronExpression) throws ParseException {
		new CronExpression(cronExpression);
	}

	protected void buildExpression(final String expression) throws ParseException {
		expressionParsed = true;
		try {
			if (seconds == null) {
				seconds = new TreeSet<>();
			}
			if (minutes == null) {
				minutes = new TreeSet<>();
			}
			if (hours == null) {
				hours = new TreeSet<>();
			}
			if (daysOfMonth == null) {
				daysOfMonth = new TreeSet<>();
			}
			if (months == null) {
				months = new TreeSet<>();
			}
			if (daysOfWeek == null) {
				daysOfWeek = new TreeSet<>();
			}
			if (years == null) {
				years = new TreeSet<>();
			}

			int exprOn = SECOND;

			final StringTokenizer exprsTok = new StringTokenizer(expression, " \t",
					false);

			while (exprsTok.hasMoreTokens() && exprOn <= YEAR) {
				final String expr = exprsTok.nextToken().trim();

				// throw an exception if L is used with other days of the month
				if (exprOn == DAY_OF_MONTH && expr.indexOf('L') != -1 && expr.length() > 1 && expr.contains(",")) {
					throw new ParseException("Support for specifying 'L' and 'LW' with other days of the month is not implemented", -1);
				}
				// throw an exception if L is used with other days of the week
				if (exprOn == DAY_OF_WEEK && expr.indexOf('L') != -1 && expr.length() > 1 && expr.contains(",")) {
					throw new ParseException("Support for specifying 'L' with other days of the week is not implemented", -1);
				}
				if (exprOn == DAY_OF_WEEK && expr.indexOf('#') != -1 && expr.indexOf('#', expr.indexOf('#') + 1) != -1) {
					throw new ParseException("Support for specifying multiple \"nth\" days is not implemented.", -1);
				}

				final StringTokenizer vTok = new StringTokenizer(expr, ",");
				while (vTok.hasMoreTokens()) {
					final String v = vTok.nextToken();
					storeExpressionVals(0, v, exprOn);
				}

				exprOn++;
			}

			if (exprOn <= DAY_OF_WEEK) {
				throw new ParseException("Unexpected end of expression.",
						expression.length());
			}

			if (exprOn <= YEAR) {
				storeExpressionVals(0, "*", YEAR);
			}

			final TreeSet<Integer> dow = getSet(DAY_OF_WEEK);
			final TreeSet<Integer> dom = getSet(DAY_OF_MONTH);

			// Copying the logic from the UnsupportedOperationException below
			final boolean dayOfMSpec = !dom.contains(NO_SPEC);
			final boolean dayOfWSpec = !dow.contains(NO_SPEC);

			if (!dayOfMSpec || dayOfWSpec) {
				if (!dayOfWSpec || dayOfMSpec) {
					throw new ParseException(
							"Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.", 0);
				}
			}
		}
		catch (final ParseException pe) {
			throw pe;
		}
		catch (final Exception e) {
			throw new ParseException("Illegal cron expression format ("
					+ e.toString() + ")", 0);
		}
	}

	protected int storeExpressionVals(final int pos, final String s, final int type)
			throws ParseException {

		int incr = 0;
		int i = skipWhiteSpace(pos, s);
		if (i >= s.length()) {
			return i;
		}
		char c = s.charAt(i);
		if ((c >= 'A') && (c <= 'Z') && (!s.equals("L")) && (!s.equals("LW")) && (!s.matches("^L-[0-9]*[W]?"))) {
			String sub = s.substring(i, i + 3);
			int sval = -1;
			int eval = -1;
			if (type == MONTH) {
				sval = getMonthNumber(sub) + 1;
				if (sval <= 0) {
					throw new ParseException("Invalid Month value: '" + sub + "'", i);
				}
				if (s.length() > i + 3 && (s.charAt(i + 3) == '-')) {
					i += 4;
					sub = s.substring(i, i + 3);
					eval = getMonthNumber(sub) + 1;
					Assert.isTrue(eval > 0, "Invalid Month value: '" + sub + "'");
				}
			}
			else if (type == DAY_OF_WEEK) {
				sval = getDayOfWeekNumber(sub);
				if (sval < 0) {
					throw new ParseException("Invalid Day-of-Week value: '"
							+ sub + "'", i);
				}
				if (s.length() > i + 3) {
					c = s.charAt(i + 3);
					if (c == '-') {
						i += 4;
						sub = s.substring(i, i + 3);
						eval = getDayOfWeekNumber(sub);
						Assert.isTrue(eval >= 0, "Invalid Day-of-Week value: '" + sub + "'");
					}
					else if (c == '#') {
						i += 4;
						nthdayOfWeek = Integer.parseInt(s.substring(i));
						Assert.isTrue(nthdayOfWeek > 0 && nthdayOfWeek < 6, "A numeric value between 1 and 5 must follow the '#' option");
					}
					else if (c == 'L') {
						lastdayOfWeek = true;
						i++;
					}
				}
			}
			else {
				throw new ParseException(
						"Illegal characters for this position: '" + sub + "'",
						i);
			}
			if (eval != -1) {
				incr = 1;
			}
			addToSet(sval, eval, incr, type);
			return (i + 3);
		}

		if (c == '?') {
			i++;
			if ((i + 1) < s.length()
					&& (s.charAt(i) != ' ' && s.charAt(i + 1) != '\t')) {
				throw new ParseException("Illegal character after '?': "
						+ s.charAt(i), i);
			}
			if (type != DAY_OF_WEEK && type != DAY_OF_MONTH) {
				throw new ParseException(
						"'?' can only be specfied for Day-of-Month or Day-of-Week.",
						i);
			}
			if (type == DAY_OF_WEEK && !lastdayOfMonth) {
				final int val = daysOfMonth.last();
				if (val == NO_SPEC_INT) {
					throw new ParseException(
							"'?' can only be specfied for Day-of-Month -OR- Day-of-Week.",
							i);
				}
			}

			addToSet(NO_SPEC_INT, -1, 0, type);
			return i;
		}

		if (c == '*' || c == '/') {
			if (c == '*' && (i + 1) >= s.length()) {
				addToSet(ALL_SPEC_INT, -1, incr, type);
				return i + 1;
			}
			else if (c == '/'
					&& ((i + 1) >= s.length() || s.charAt(i + 1) == ' ' || s
					.charAt(i + 1) == '\t')) {
				throw new ParseException("'/' must be followed by an integer.", i);
			}
			else if (c == '*') {
				i++;
			}
			c = s.charAt(i);
			if (c == '/') { // is an increment specified?
				i++;
				if (i >= s.length()) {
					throw new ParseException("Unexpected end of string.", i);
				}

				incr = getNumericValue(s, i);

				i++;
				if (incr > 10) {
					i++;
				}
				if (incr > 59 && (type == SECOND || type == MINUTE)) {
					throw new ParseException("Increment > 60 : " + incr, i);
				}
				else if (incr > 23 && (type == HOUR)) {
					throw new ParseException("Increment > 24 : " + incr, i);
				}
				else if (incr > 31 && (type == DAY_OF_MONTH)) {
					throw new ParseException("Increment > 31 : " + incr, i);
				}
				else if (incr > 7 && (type == DAY_OF_WEEK)) {
					throw new ParseException("Increment > 7 : " + incr, i);
				}
				else if (incr > 12 && (type == MONTH)) {
					throw new ParseException("Increment > 12 : " + incr, i);
				}
			}
			else {
				incr = 1;
			}

			addToSet(ALL_SPEC_INT, -1, incr, type);
			return i;
		}
		else if (c == 'L') {
			i++;
			if (type == DAY_OF_MONTH) {
				lastdayOfMonth = true;
			}
			if (type == DAY_OF_WEEK) {
				addToSet(7, 7, 0, type);
			}
			if (type == DAY_OF_MONTH && s.length() > i) {
				c = s.charAt(i);
				if (c == '-') {
					final ValueSet vs = getValue(0, s, i + 1);
					lastdayOffset = vs.value;
					if (lastdayOffset > 30) {
						throw new ParseException("Offset from last day must be <= 30", i + 1);
					}
					i = vs.pos;
				}
				if (s.length() > i) {
					c = s.charAt(i);
					if (c == 'W') {
						nearestWeekday = true;
						i++;
					}
				}
			}
			return i;
		}
		else if (c >= '0' && c <= '9') {
			int val = Integer.parseInt(String.valueOf(c));
			i++;
			if (i >= s.length()) {
				addToSet(val, -1, -1, type);
			}
			else {
				c = s.charAt(i);
				if (c >= '0' && c <= '9') {
					final ValueSet vs = getValue(val, s, i);
					val = vs.value;
					i = vs.pos;
				}
				i = checkNext(i, s, val, type);
				return i;
			}
		}
		else {
			throw new ParseException("Unexpected character: " + c, i);
		}

		return i;
	}

	protected int checkNext(final int pos, final String s, final int val, final int type)
			throws ParseException {

		int end = -1;
		int i = pos;

		if (i >= s.length()) {
			addToSet(val, end, -1, type);
			return i;
		}

		char c = s.charAt(pos);

		if (c == 'L') {
			if (type == DAY_OF_WEEK) {
				if (val < 1 || val > 7) {
					throw new ParseException("Day-of-Week values must be between 1 and 7", -1);
				}
				lastdayOfWeek = true;
			}
			else {
				throw new ParseException("'L' option is not valid here. (pos=" + i + ")", i);
			}
			final TreeSet<Integer> set = getSet(type);
			set.add(val);
			i++;
			return i;
		}

		if (c == 'W') {
			if (type == DAY_OF_MONTH) {
				nearestWeekday = true;
			}
			else {
				throw new ParseException("'W' option is not valid here. (pos=" + i + ")", i);
			}
			if (val > 31) {
				throw new ParseException("The 'W' option does not make sense with values larger than 31 (max number of days in a month)", i);
			}
			final TreeSet<Integer> set = getSet(type);
			set.add(val);
			i++;
			return i;
		}

		if (c == '#') {
			if (type != DAY_OF_WEEK) {
				throw new ParseException("'#' option is not valid here. (pos=" + i + ")", i);
			}
			i++;
			try {
				nthdayOfWeek = Integer.parseInt(s.substring(i));
				if (nthdayOfWeek < 1 || nthdayOfWeek > 5) {
					throw new Exception();
				}
			}
			catch (final Exception e) {
				throw new ParseException(
						"A numeric value between 1 and 5 must follow the '#' option",
						i);
			}

			final TreeSet<Integer> set = getSet(type);
			set.add(val);
			i++;
			return i;
		}

		if (c == '-') {
			i++;
			c = s.charAt(i);
			final int v = Integer.parseInt(String.valueOf(c));
			end = v;
			i++;
			if (i >= s.length()) {
				addToSet(val, end, 1, type);
				return i;
			}
			c = s.charAt(i);
			if (c >= '0' && c <= '9') {
				final ValueSet vs = getValue(v, s, i);
				end = vs.value;
				i = vs.pos;
			}
			if (i < s.length() && (s.charAt(i) == '/')) {
				i++;
				c = s.charAt(i);
				final int v2 = Integer.parseInt(String.valueOf(c));
				i++;
				if (i >= s.length()) {
					addToSet(val, end, v2, type);
					return i;
				}
				c = s.charAt(i);
				if (c >= '0' && c <= '9') {
					final ValueSet vs = getValue(v2, s, i);
					final int v3 = vs.value;
					addToSet(val, end, v3, type);
					i = vs.pos;
					return i;
				}
				else {
					addToSet(val, end, v2, type);
					return i;
				}
			}
			else {
				addToSet(val, end, 1, type);
				return i;
			}
		}

		if (c == '/') {
			i++;
			c = s.charAt(i);
			final int v2 = Integer.parseInt(String.valueOf(c));
			i++;
			if (i >= s.length()) {
				addToSet(val, end, v2, type);
				return i;
			}
			c = s.charAt(i);
			if (c >= '0' && c <= '9') {
				final ValueSet vs = getValue(v2, s, i);
				final int v3 = vs.value;
				addToSet(val, end, v3, type);
				i = vs.pos;
				return i;
			}
			else {
				throw new ParseException("Unexpected character '" + c + "' after '/'", i);
			}
		}

		addToSet(val, end, 0, type);
		i++;
		return i;
	}

	public String getCronExpression() {
		return cronExpression;
	}

	public String getExpressionSummary() {
		final StringBuilder buf = new StringBuilder();

		buf.append("seconds: ");
		buf.append(getExpressionSetSummary(seconds));
		buf.append("\n");
		buf.append("minutes: ");
		buf.append(getExpressionSetSummary(minutes));
		buf.append("\n");
		buf.append("hours: ");
		buf.append(getExpressionSetSummary(hours));
		buf.append("\n");
		buf.append("daysOfMonth: ");
		buf.append(getExpressionSetSummary(daysOfMonth));
		buf.append("\n");
		buf.append("months: ");
		buf.append(getExpressionSetSummary(months));
		buf.append("\n");
		buf.append("daysOfWeek: ");
		buf.append(getExpressionSetSummary(daysOfWeek));
		buf.append("\n");
		buf.append("lastdayOfWeek: ");
		buf.append(lastdayOfWeek);
		buf.append("\n");
		buf.append("nearestWeekday: ");
		buf.append(nearestWeekday);
		buf.append("\n");
		buf.append("NthDayOfWeek: ");
		buf.append(nthdayOfWeek);
		buf.append("\n");
		buf.append("lastdayOfMonth: ");
		buf.append(lastdayOfMonth);
		buf.append("\n");
		buf.append("years: ");
		buf.append(getExpressionSetSummary(years));
		buf.append("\n");

		return buf.toString();
	}

	protected String getExpressionSetSummary(final java.util.Set<Integer> set) {

		if (set.contains(NO_SPEC)) {
			return "?";
		}
		if (set.contains(ALL_SPEC)) {
			return "*";
		}

		final StringBuilder buf = new StringBuilder();

		final Iterator<Integer> itr = set.iterator();
		boolean first = true;
		while (itr.hasNext()) {
			final Integer iVal = itr.next();
			final String val = iVal.toString();
			if (!first) {
				buf.append(",");
			}
			buf.append(val);
			first = false;
		}

		return buf.toString();
	}

	protected String getExpressionSetSummary(final java.util.ArrayList<Integer> list) {

		if (list.contains(NO_SPEC)) {
			return "?";
		}
		if (list.contains(ALL_SPEC)) {
			return "*";
		}

		final StringBuilder buf = new StringBuilder();

		final Iterator<Integer> itr = list.iterator();
		boolean first = true;
		while (itr.hasNext()) {
			final Integer iVal = itr.next();
			final String val = iVal.toString();
			if (!first) {
				buf.append(",");
			}
			buf.append(val);
			first = false;
		}

		return buf.toString();
	}

	protected int skipWhiteSpace(int i, final String s) {
		for (; i < s.length() && (s.charAt(i) == ' ' || s.charAt(i) == '\t'); i++) {
			// empty
		}

		return i;
	}

	protected int findNextWhiteSpace(int i, final String s) {
		for (; i < s.length() && (s.charAt(i) != ' ' || s.charAt(i) != '\t'); i++) {
			// empty
		}

		return i;
	}

	protected void addToSet(final int val, final int end, int incr, final int type)
			throws ParseException {

		final TreeSet<Integer> set = getSet(type);

		if (type == SECOND || type == MINUTE) {
			if ((val < 0 || val > 59 || end > 59) && (val != ALL_SPEC_INT)) {
				throw new ParseException(
						"Minute and Second values must be between 0 and 59",
						-1);
			}
		}
		else if (type == HOUR) {
			if ((val < 0 || val > 23 || end > 23) && (val != ALL_SPEC_INT)) {
				throw new ParseException(
						"Hour values must be between 0 and 23", -1);
			}
		}
		else if (type == DAY_OF_MONTH) {
			if ((val < 1 || val > 31 || end > 31) && (val != ALL_SPEC_INT)
					&& (val != NO_SPEC_INT)) {
				throw new ParseException(
						"Day of month values must be between 1 and 31", -1);
			}
		}
		else if (type == MONTH) {
			if ((val < 1 || val > 12 || end > 12) && (val != ALL_SPEC_INT)) {
				throw new ParseException(
						"Month values must be between 1 and 12", -1);
			}
		}
		else if (type == DAY_OF_WEEK) {
			if ((val == 0 || val > 7 || end > 7) && (val != ALL_SPEC_INT)
					&& (val != NO_SPEC_INT)) {
				throw new ParseException(
						"Day-of-Week values must be between 1 and 7", -1);
			}
		}

		if ((incr == 0 || incr == -1) && val != ALL_SPEC_INT) {
			if (val != -1) {
				set.add(val);
			}
			else {
				set.add(NO_SPEC);
			}

			return;
		}

		int startAt = val;
		int stopAt = end;

		if (val == ALL_SPEC_INT && incr <= 0) {
			incr = 1;
			set.add(ALL_SPEC); // put in a marker, but also fill values
		}

		if (type == SECOND || type == MINUTE) {
			if (stopAt == -1) {
				stopAt = 59;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 0;
			}
		}
		else if (type == HOUR) {
			if (stopAt == -1) {
				stopAt = 23;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 0;
			}
		}
		else if (type == DAY_OF_MONTH) {
			if (stopAt == -1) {
				stopAt = 31;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1;
			}
		}
		else if (type == MONTH) {
			if (stopAt == -1) {
				stopAt = 12;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1;
			}
		}
		else if (type == DAY_OF_WEEK) {
			if (stopAt == -1) {
				stopAt = 7;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1;
			}
		}
		else if (type == YEAR) {
			if (stopAt == -1) {
				stopAt = MAX_YEAR;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1970;
			}
		}

		// if the end of the range is before the start, then we need to overflow into
		// the next day, month etc. This is done by adding the maximum amount for that
		// type, and using modulus max to determine the value being added.
		int max = -1;
		if (stopAt < startAt) {
			switch (type) {
				case SECOND:
					max = 60;
					break;
				case MINUTE:
					max = 60;
					break;
				case HOUR:
					max = 24;
					break;
				case MONTH:
					max = 12;
					break;
				case DAY_OF_WEEK:
					max = 7;
					break;
				case DAY_OF_MONTH:
					max = 31;
					break;
				case YEAR:
					throw new IllegalArgumentException("Start year must be less than stop year");
				default:
					throw new IllegalArgumentException("Unexpected type encountered");
			}
			stopAt += max;
		}

		for (int i = startAt; i <= stopAt; i += incr) {
			if (max == -1) {
				// ie: there's no max to overflow over
				set.add(i);
			}
			else {
				// take the modulus to get the real value
				int i2 = i % max;

				// 1-indexed ranges should not include 0, and should include their max
				if (i2 == 0 && (type == MONTH || type == DAY_OF_WEEK || type == DAY_OF_MONTH)) {
					i2 = max;
				}

				set.add(i2);
			}
		}
	}

	TreeSet<Integer> getSet(final int type) throws ParseException {
		switch (type) {
			case SECOND:
				return seconds;
			case MINUTE:
				return minutes;
			case HOUR:
				return hours;
			case DAY_OF_MONTH:
				return daysOfMonth;
			case MONTH:
				return months;
			case DAY_OF_WEEK:
				return daysOfWeek;
			case YEAR:
				return years;
			default:
				throw new ParseException("Invalid type value: '" + type + "'", -1);
		}
	}

	protected ValueSet getValue(final int v, final String s, int i) {
		char c = s.charAt(i);
		final StringBuilder s1 = new StringBuilder(String.valueOf(v));
		while (c >= '0' && c <= '9') {
			s1.append(c);
			i++;
			if (i >= s.length()) {
				break;
			}
			c = s.charAt(i);
		}
		final ValueSet val = new ValueSet();

		val.pos = (i < s.length()) ? i : i + 1;
		val.value = Integer.parseInt(s1.toString());
		return val;
	}

	protected int getNumericValue(final String s, final int i) {
		final int endOfVal = findNextWhiteSpace(i, s);
		final String val = s.substring(i, endOfVal);
		return Integer.parseInt(val);
	}

	protected int getMonthNumber(final String s) {
		final Integer integer = monthMap.get(s);

		if (integer == null) {
			return -1;
		}

		return integer;
	}

	protected int getDayOfWeekNumber(final String s) {
		final Integer integer = dayMap.get(s);

		if (integer == null) {
			return -1;
		}

		return integer;
	}

	public Date getTimeAfter(Date afterTime) {

		// Computation is based on Gregorian year only.
		final Calendar cl = new java.util.GregorianCalendar(getTimeZone());

		// move ahead one second, since we're computing the time *after* the
		// given time
		if (afterTime == null) {
			return null;
		}
		afterTime = new Date(afterTime.getTime() + 1000);
		// CronTrigger does not deal with milliseconds
		cl.setTime(afterTime);
		cl.set(Calendar.MILLISECOND, 0);

		boolean gotOne = false;
		// loop until we've computed the next time, or we've past the endTime
		while (!gotOne) {
			//if (endTime != null && cl.getTime().after(endTime)) return null;
			if (cl.get(Calendar.YEAR) > 2999) { // prevent endless loop...
				return null;
			}

			SortedSet<Integer> st = null;
			int t = 0;

			int sec = cl.get(Calendar.SECOND);
			int min = cl.get(Calendar.MINUTE);

			// get second.................................................
			st = seconds.tailSet(sec);
			if (st != null && st.size() != 0) {
				sec = st.first();
			}
			else {
				sec = seconds.first();
				min++;
				cl.set(Calendar.MINUTE, min);
			}
			cl.set(Calendar.SECOND, sec);

			min = cl.get(Calendar.MINUTE);
			int hr = cl.get(Calendar.HOUR_OF_DAY);
			t = -1;

			// get minute.................................................
			st = minutes.tailSet(min);
			if (st != null && st.size() != 0) {
				t = min;
				min = st.first();
			}
			else {
				min = minutes.first();
				hr++;
			}
			if (min != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, min);
				setCalendarHour(cl, hr);
				continue;
			}
			cl.set(Calendar.MINUTE, min);

			hr = cl.get(Calendar.HOUR_OF_DAY);
			int day = cl.get(Calendar.DAY_OF_MONTH);
			t = -1;

			// get hour...................................................
			st = hours.tailSet(hr);
			if (st != null && st.size() != 0) {
				t = hr;
				hr = st.first();
			}
			else {
				hr = hours.first();
				day++;
			}
			if (hr != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, 0);
				cl.set(Calendar.DAY_OF_MONTH, day);
				setCalendarHour(cl, hr);
				continue;
			}
			cl.set(Calendar.HOUR_OF_DAY, hr);

			day = cl.get(Calendar.DAY_OF_MONTH);
			int mon = cl.get(Calendar.MONTH) + 1;
			// '+ 1' because calendar is 0-based for this field, and we are
			// 1-based
			t = -1;
			int tmon = mon;

			// get day...................................................
			final boolean dayOfMSpec = !daysOfMonth.contains(NO_SPEC);
			final boolean dayOfWSpec = !daysOfWeek.contains(NO_SPEC);
			if (dayOfMSpec && !dayOfWSpec) { // get day by day of month rule
				st = daysOfMonth.tailSet(day);
				if (lastdayOfMonth) {
					if (!nearestWeekday) {
						t = day;
						day = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
						day -= lastdayOffset;
						day = t > day ? 1 : day;
						if (t > day && ++mon > 12) {
							mon = 1;
							tmon = 3333; // ensure test of mon != tmon further below fails
							cl.add(Calendar.YEAR, 1);
						}
					}
					else {
						t = day;
						day = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
						day -= lastdayOffset;

						final Calendar tcal = Calendar.getInstance(getTimeZone());
						tcal.set(Calendar.SECOND, 0);
						tcal.set(Calendar.MINUTE, 0);
						tcal.set(Calendar.HOUR_OF_DAY, 0);
						tcal.set(Calendar.DAY_OF_MONTH, day);
						tcal.set(Calendar.MONTH, mon - 1);
						tcal.set(Calendar.YEAR, cl.get(Calendar.YEAR));

						final int ldom = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
						final int dow = tcal.get(Calendar.DAY_OF_WEEK);

						if (dow == Calendar.SATURDAY && day == 1) {
							day += 2;
						}
						else if (dow == Calendar.SATURDAY) {
							day -= 1;
						}
						else if (dow == Calendar.SUNDAY && day == ldom) {
							day -= 2;
						}
						else if (dow == Calendar.SUNDAY) {
							day += 1;
						}

						tcal.set(Calendar.SECOND, sec);
						tcal.set(Calendar.MINUTE, min);
						tcal.set(Calendar.HOUR_OF_DAY, hr);
						tcal.set(Calendar.DAY_OF_MONTH, day);
						tcal.set(Calendar.MONTH, mon - 1);
						final Date nTime = tcal.getTime();
						if (nTime.before(afterTime)) {
							day = 1;
							mon++;
						}
					}
				}
				else if (nearestWeekday) {
					t = day;
					day = daysOfMonth.first();

					final Calendar tcal = Calendar.getInstance(getTimeZone());
					tcal.set(Calendar.SECOND, 0);
					tcal.set(Calendar.MINUTE, 0);
					tcal.set(Calendar.HOUR_OF_DAY, 0);
					tcal.set(Calendar.DAY_OF_MONTH, day);
					tcal.set(Calendar.MONTH, mon - 1);
					tcal.set(Calendar.YEAR, cl.get(Calendar.YEAR));

					final int ldom = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
					final int dow = tcal.get(Calendar.DAY_OF_WEEK);

					if (dow == Calendar.SATURDAY && day == 1) {
						day += 2;
					}
					else if (dow == Calendar.SATURDAY) {
						day -= 1;
					}
					else if (dow == Calendar.SUNDAY && day == ldom) {
						day -= 2;
					}
					else if (dow == Calendar.SUNDAY) {
						day += 1;
					}

					tcal.set(Calendar.SECOND, sec);
					tcal.set(Calendar.MINUTE, min);
					tcal.set(Calendar.HOUR_OF_DAY, hr);
					tcal.set(Calendar.DAY_OF_MONTH, day);
					tcal.set(Calendar.MONTH, mon - 1);
					final Date nTime = tcal.getTime();
					if (nTime.before(afterTime)) {
						day = daysOfMonth.first();
						mon++;
					}
				}
				else if (st != null && st.size() != 0) {
					t = day;
					day = st.first();
					// make sure we don't over-run a short month, such as february
					final int lastDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
					if (day > lastDay) {
						day = daysOfMonth.first();
						mon++;
					}
				}
				else {
					day = daysOfMonth.first();
					mon++;
				}

				if (day != t || mon != tmon) {
					cl.set(Calendar.SECOND, 0);
					cl.set(Calendar.MINUTE, 0);
					cl.set(Calendar.HOUR_OF_DAY, 0);
					cl.set(Calendar.DAY_OF_MONTH, day);
					cl.set(Calendar.MONTH, mon - 1);
					// '- 1' because calendar is 0-based for this field, and we
					// are 1-based
					continue;
				}
			}
			else if (dayOfWSpec && !dayOfMSpec) { // get day by day of week rule
				if (lastdayOfWeek) { // are we looking for the last XXX day of
					// the month?
					final int dow = daysOfWeek.first(); // desired
					// d-o-w
					final int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
					int daysToAdd = 0;
					if (cDow < dow) {
						daysToAdd = dow - cDow;
					}
					if (cDow > dow) {
						daysToAdd = dow + (7 - cDow);
					}

					final int lDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));

					if (day + daysToAdd > lDay) { // did we already miss the
						// last one?
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, 1);
						cl.set(Calendar.MONTH, mon);
						// no '- 1' here because we are promoting the month
						continue;
					}

					// find date of last occurrence of this day in this month...
					while ((day + daysToAdd + 7) <= lDay) {
						daysToAdd += 7;
					}
					day += daysToAdd;
					if (daysToAdd > 0) {
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, day);
						cl.set(Calendar.MONTH, mon - 1);
						// '- 1' here because we are not promoting the month
						continue;
					}
				}
				else if (nthdayOfWeek != 0) {
					// are we looking for the Nth XXX day in the month?
					final int dow = daysOfWeek.first(); // desired
					// d-o-w
					final int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
					int daysToAdd = 0;
					if (cDow < dow) {
						daysToAdd = dow - cDow;
					}
					else if (cDow > dow) {
						daysToAdd = dow + (7 - cDow);
					}

					boolean dayShifted = false;
					if (daysToAdd > 0) {
						dayShifted = true;
					}

					day += daysToAdd;
					int weekOfMonth = day / 7;
					if (day % 7 > 0) {
						weekOfMonth++;
					}

					daysToAdd = (nthdayOfWeek - weekOfMonth) * 7;
					day += daysToAdd;
					if (daysToAdd < 0
							|| day > getLastDayOfMonth(mon, cl
							.get(Calendar.YEAR))) {
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, 1);
						cl.set(Calendar.MONTH, mon);
						// no '- 1' here because we are promoting the month
						continue;
					}
					else if (daysToAdd > 0 || dayShifted) {
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, day);
						cl.set(Calendar.MONTH, mon - 1);
						// '- 1' here because we are NOT promoting the month
						continue;
					}
				}
				else {
					final int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
					int dow = daysOfWeek.first(); // desired
					// d-o-w
					st = daysOfWeek.tailSet(cDow);
					if (st != null && st.size() > 0) {
						dow = st.first();
					}

					int daysToAdd = 0;
					if (cDow < dow) {
						daysToAdd = dow - cDow;
					}
					if (cDow > dow) {
						daysToAdd = dow + (7 - cDow);
					}

					final int lDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));

					if (day + daysToAdd > lDay) { // will we pass the end of
						// the month?
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, 1);
						cl.set(Calendar.MONTH, mon);
						// no '- 1' here because we are promoting the month
						continue;
					}
					else if (daysToAdd > 0) { // are we switching days?
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, day + daysToAdd);
						cl.set(Calendar.MONTH, mon - 1);
						// '- 1' because calendar is 0-based for this field,
						// and we are 1-based
						continue;
					}
				}
			}
			else { // dayOfWSpec && !dayOfMSpec
				throw new UnsupportedOperationException(
						"Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.");
			}
			cl.set(Calendar.DAY_OF_MONTH, day);

			mon = cl.get(Calendar.MONTH) + 1;
			// '+ 1' because calendar is 0-based for this field, and we are
			// 1-based
			int year = cl.get(Calendar.YEAR);
			t = -1;

			// test for expressions that never generate a valid fire date,
			// but keep looping...
			if (year > MAX_YEAR) {
				return null;
			}

			// get month...................................................
			st = months.tailSet(mon);
			if (st != null && st.size() != 0) {
				t = mon;
				mon = st.first();
			}
			else {
				mon = months.first();
				year++;
			}
			if (mon != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, 0);
				cl.set(Calendar.HOUR_OF_DAY, 0);
				cl.set(Calendar.DAY_OF_MONTH, 1);
				cl.set(Calendar.MONTH, mon - 1);
				// '- 1' because calendar is 0-based for this field, and we are
				// 1-based
				cl.set(Calendar.YEAR, year);
				continue;
			}
			cl.set(Calendar.MONTH, mon - 1);
			// '- 1' because calendar is 0-based for this field, and we are
			// 1-based

			year = cl.get(Calendar.YEAR);
			t = -1;

			// get year...................................................
			st = years.tailSet(year);
			if (st != null && st.size() != 0) {
				t = year;
				year = st.first();
			}
			else {
				return null; // ran out of years...
			}

			if (year != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, 0);
				cl.set(Calendar.HOUR_OF_DAY, 0);
				cl.set(Calendar.DAY_OF_MONTH, 1);
				cl.set(Calendar.MONTH, 0);
				// '- 1' because calendar is 0-based for this field, and we are
				// 1-based
				cl.set(Calendar.YEAR, year);
				continue;
			}
			cl.set(Calendar.YEAR, year);

			gotOne = true;
		} // while( !done )

		return cl.getTime();
	}

	/**
	 * Advance the calendar to the particular hour paying particular attention
	 * to daylight saving problems.
	 *
	 * @param cal  the calendar to operate on
	 * @param hour the hour to set
	 */
	protected void setCalendarHour(final Calendar cal, final int hour) {
		cal.set(Calendar.HOUR_OF_DAY, hour);
		if (cal.get(Calendar.HOUR_OF_DAY) != hour && hour != 24) {
			cal.set(Calendar.HOUR_OF_DAY, hour + 1);
		}
	}

	protected Date getTimeBefore(final Date targetDate) {
		final Calendar cl = Calendar.getInstance(getTimeZone());

		// CronTrigger does not deal with milliseconds, so truncate target
		cl.setTime(targetDate);
		cl.set(Calendar.MILLISECOND, 0);
		final Date targetDateNoMs = cl.getTime();

		// to match this
		Date start = targetDateNoMs;
		final long minIncrement = findMinIncrement();
		Date prevFireTime;
		do {
			final Date prevCheckDate = new Date(start.getTime() - minIncrement);
			prevFireTime = getTimeAfter(prevCheckDate);
			if (prevFireTime == null || prevFireTime.before(MIN_DATE)) {
				return null;
			}
			start = prevCheckDate;
		} while (prevFireTime.compareTo(targetDateNoMs) >= 0);
		return prevFireTime;
	}

	public Date getPrevFireTime(final Date targetDate) {
		return getTimeBefore(targetDate);
	}

	private long findMinIncrement() {
		if (seconds.size() != 1) {
			return minInSet(seconds) * 1000;
		}
		else if (seconds.first() == ALL_SPEC_INT) {
			return 1000;
		}
		if (minutes.size() != 1) {
			return minInSet(minutes) * 60000;
		}
		else if (minutes.first() == ALL_SPEC_INT) {
			return 60000;
		}
		if (hours.size() != 1) {
			return minInSet(hours) * 3600000;
		}
		else if (hours.first() == ALL_SPEC_INT) {
			return 3600000;
		}
		return 86400000;
	}

	private int minInSet(final TreeSet<Integer> set) {
		int previous = 0;
		int min = Integer.MAX_VALUE;
		boolean first = true;
		for (final int value : set) {
			if (first) {
				previous = value;
				first = false;
				continue;
			}
			else {
				final int diff = value - previous;
				if (diff < min) {
					min = diff;
				}
			}
		}
		return min;
	}

	protected boolean isLeapYear(final int year) {
		return ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0));
	}

	protected int getLastDayOfMonth(final int monthNum, final int year) {
		switch (monthNum) {
			case 1:
				return 31;
			case 2:
				return (isLeapYear(year)) ? 29 : 28;
			case 3:
				return 31;
			case 4:
				return 30;
			case 5:
				return 31;
			case 6:
				return 30;
			case 7:
				return 31;
			case 8:
				return 31;
			case 9:
				return 30;
			case 10:
				return 31;
			case 11:
				return 30;
			case 12:
				return 31;
			default:
				throw new IllegalArgumentException("Illegal month number: "
						+ monthNum);
		}
	}

	private class ValueSet {
		public int value;
		public int pos;
	}
}
